In recent years, there has been an increase in people suffering from lifestyle-related diseases such as diabetes, and hence there has been an increase in the need to measure blood sugar level, cholesterol level and so on in one's blood based on a simple technique that can be carried out at home and so on. As a simple technique for measuring blood sugar level, there is for example a method in which a fingertip is punctured so that blood flows out and a sample is taken, and then the glucose concentration in the blood is measured using this sample.
However, puncturing one's fingertip is accompanied by pain, and hence measuring the blood sugar level may be painful. In particular, in the case of a diabetes sufferer, to carry out blood sugar level management during everyday life, the blood sugar level must be measured several times a day. A diabetes sufferer may thus be subjected to pain several times a day, and hence measuring the blood sugar level is a great burden for a diabetes sufferer. Moreover, with ordinary glucose concentration measurement, there is a problem that consumables such as biosensors or urine test paper are used.
In Japanese Patent Application Laid-open No. H05-176917, to reduce the burden during glucose concentration measurement, there has thus been disclosed a method of measuring the blood sugar level without taking blood from a patient. With this method, near-infrared light of wavelength 0.78 to 1.32 μm is irradiated onto a human body, and the glucose concentration can be measured based on the intensity of the light transmitted through the human body.
On the other hand, in Japanese Patent Application Laid-open No. H09-138231, there has been disclosed a method of measuring the glucose concentration in urine without the need for consumables such as urine test paper. With this method, light that has passed through a polarizer is irradiated onto a sample solution, and the glucose concentration can be measured based on the angle of optical rotation of the light transmitted through the sample solution at this time.
However, with the method disclosed in Japanese Patent Application Laid-open No. 5-176917, the measurement is prone to being affected by the state of optical scattering when the irradiated light is transmitted through the human body. That is, variation in measurement results between individuals arises due to differences in the state of optical scattering between individuals, and moreover even with the same person, variation in measurement results arises due to differences in the state of optical scattering at different measurement sites. To resolve these problems, a calibration line must be prepared for each individual, and moreover for each person measurement must be always be carried out at the same site.
On the other hand, with the method disclosed in Japanese Patent Application Laid-open No. H09-138231, the method is effective for measurement on a solution that does not contain solid matter, but there is a problem in that in the case of trying to carry out measurement on a turbid liquid such as blood or trying to measure a component in biological tissue, the measurement is affected by optical scattering due to solid matter in the object of measurement, and hence accurate measurements cannot be obtained.